7211 Clinical and Molecular Characterization Of An Aldosterone-Producing Adenoma Harboring Double Somatic Mutations In CTNNB1 and GNA11

Abstract Disclosure: A. Blinder: None. K. Nanba: Grant Recipient; Self; AstraZeneca. A. Udager: None. Y. Hirokawa: None. T. Miura: None. H. Okuno: None. K. Moriyoshi: None. Y. Yamazaki: None. H. Sasano: None. A. Yasoda: None. N. Satoh-Asahara: None. W.E. Rainey: None. T. Tagami: None. Background: Somatic activating mutations in CTNNB1, encoding β-catenin, have been detected in a small subset of aldosterone-producing adenomas (APAs). As a possible pathogenesis, an association of CTNNB1-mutated APA with pregnancy and menopause has been proposed. A recent study reported double somatic mutations in CTNNB1 and GNA11/Q, encoding guanine nucleotide-binding protein subunits alpha-11 and alpha-Q, in APA. However, due to its rare incidence, clinical and molecular features of APA associated with these mutations have not been well characterized. Herein, we report a case of APA harboring somatic CTNNB1 and GNA11 mutations. Clinical Case: A 46-year-old Japanese woman presented with hypertension and hypokalemia. She had two pregnancies in the past but had no history of pregnancy-induced hypertension. She had regular menstrual cycles at presentation. Laboratory testing showed elevated plasma aldosterone concentration with suppressed plasma renin activity. She was diagnosed as having primary aldosteronism based on the results of a captopril challenge test. Adrenal computed tomography revealed a 2 cm right adrenal mass. Adrenal venous sampling indicated excess aldosterone production from the right adrenal gland. She underwent right laparoscopic adrenalectomy. Histologic diagnosis of the resected tumor was adrenocortical adenoma based on the criteria of Weiss. Notably, Ki-67 labeling index was high (6% at hotspots). After surgery, her blood pressure and serum potassium both normalized. According to the primary aldosteronism surgical outcome (PASO) study criteria, PA remained clinically and biochemically cured at follow-up 2.5 years after surgery. Results: Immunohistochemistry (IHC) showed high and diffuse expression of aldosterone synthase (CYP11B2) within the tumor, whereas immunoreactivity of 17α-hydroxylase (CYP17A1) and 11β-hydroxylase (CYP11B1), both required for cortisol biosynthesis, was markedly low. VSNL1, a marker for the zona glomerulosa (ZG) where physiologic aldosterone biosynthesis occurs, was highly expressed within the tumor. CYP11B2 IHC-guided tumor capture followed by targeted next-generation sequencing identified double somatic CTNNB1 (p.D32Y) and GNA11 (p.Q209H) mutations. Quantitative real-time RT-PCR revealed high tumor expression of LHCGR (LH receptor) and GNRHR (GNRH receptor) mRNA levels compared with those in adjacent normal adrenal (148-fold and 56-fold, respectively). Immunofluorescence staining of the tumor revealed the presence of activated β-catenin, consistent with features of the normal ZG. Conclusions: Our study indicates that an APA with double somatic mutations in CTNNB1 and GNA11 has characteristics of the ZG and could occur in adults with no clear association with pregnancy or menopause. Presentation: 6/3/2024